We propose a 36-month project to conduct a QUAL/quan mixed methods study of nonmedical prescription stimulant users in San Francisco. We define nonmedical prescription stimulant use as the use of prescription stimulants in a manner other than prescribed, including use for cognitive performance enhancement, recreational purposes, or to self-medicate for ADHD-type or other problems. Nonmedical use of prescription stimulants among college students has been well documented. To date, research studies ignore an entire population of non students who use nonmedical prescription stimulants as performance enhancers for work or recreation. What we do not know is how older adults use prescription stimulants nonmedically. Thus, we will conduct a QUAL/quan mixed method study of the experiences of nonmedical prescription stimulant users in three age cohorts. Using an adaptive intersectionality theoretical framework, we will conduct in-depth qualitative interviews with 150 participants. Fifty will be between 18 - 25 years of age, fifty 26 - 45 year olds who make up the first cohort (beginning in 1994) of recipients of ADHD medications, and fifty who are 46 and older. All participants will have used prescription stimulants nonmedically at least six times in the twelve months prior to interview. We will examine the types of prescription stimulants and the use of other prescription drugs and/or street drugs or alcohol to counter or enhance the effects of prescription stimulants. We will explore the intersection of individual factors, includig life stage and social location that contribute to decisions to use prescription stimulants nonmedically, motivations to use, knowledge about risks and benefits of prescription stimulant use, any adverse health or social consequences experienced, availability and diversion of prescription stimulants, differences in attitudes and behaviors relating to nonmedical prescription stimulant use and differences among the various age groups concerning all of the above. Findings will contribute to our understandings of users' experiences, including motivations to use, decision-making processes, perceptions of risk, health and social consequences of use, sources of prescription stimulants, and impact of age cohort on all of the above.